Process of isomekizing isomelabunes



Patented Sept. 13, 1949 UNITED STATES PATENT OFFICE 2,482,076 PROCESS OFISOMEHIZING ISOMELAMINES Jack '1. Thurston,

Riverside, Conn, assignor to American Cyanamid Company,

New York,

N. Y., a corporation of Maine No Drawing. Application March 9, 1945,

Serial 7 Claims. (Cl. 260-42495) This invention relates to a method ofpreparing substituted-melamines by isomerization of substitutedisomelamines.

I have discovered that mono-substituted-isomelamines having the formula:

IYH:

by merely heating the isomelamine in an hydroxylated organic solvent attemperatures of 80 0., or higher, in the presence of catalytic amountsof a strong basic substance. The yields, in many cases, approachtheoretical.

The mono-substituted-isomelamines which may be isomerized in accordancewith the present inventi'on -are new compounds but they may be preparedby reacting together a strong acid, and 1,3-di'cyanoguanidine in themanner described and ol'airrled in the oopending application of DonaldW. Kaiser and Daniel E. Nagy, Serial No. 554,155, filed September 1 1944.

Preparation of representative isomelam-ines will be describedhereinafter.

Suitable 'isemelamines which may be prepared and converted into thecorresponding normal melamines by the process of the present inventioninclude phenylisomelamine, p-ethoxyphenyliso melamine,o-bromophenylisomelamine, 2,541 chlorophenylisomelamine,ohydroxyphenylisomelamine, m-nitrophenylisomelamine,p-nitrophenylisomelamine, p-arsonophenylisomelamine,2'-"methyl-4-isopropylphenylisomelamine, 'o-tolylisomelamine,p-sulfonamidophenylisomelamine, alpha-naphthylisomelamine,p-aminophenylisomelamine and p=phenylenediisomelamine,p-sulfophenylisomelamine, butylisomelamine, ethylisomelamine,laurylisomelamine, beta-hydroxyethylisomelami'ne, and others of similarcharacter. As will be apparent from the foregoing, 'R in the formula maybe an aliphatic, cycloaliphatic, or aromatic radical.

The solvent, or organic liquid, "in which the,

primary amine, a :5

- alcohol if desired.

' slum hydroxide, sodium isomerization is carried out is an hydroxylatedorganic liquid, such as ethyl alcohol, butyl alcohol, isopropyl alcohol,amyl alcohol, octyl alcohol, ethylene glycol, the monoethyl ether ofethylene glycol and other mono-ethers of like character, glycerol, andthe like. The preferred alcohols have a boiling point of at least 80 C.although those having a lower boiling point may be employed if theisomerization is conducted in pressure vessels. It is also preferred,but not necessary that the alcohol be a liquid so that the product maybe easily separated therefrom by filtration or other known means.Dioxane and other inert solvents may be used as diluents for the Thepresence of substantial the reaction mixture is to be to cause formationof side amounts of water in avoided as water tends reaction products.

The catalytic agent is a strongly alkaline substance having a basicityat least that of the isomelamine to be isomerized. The isomelamines aremoderately strong alkaline substances having a pH in aqueous solutionabove about 11. Suitable catalysts include sodium hydroxide,potasmethoxide, potassium methoxide, sodium ethoxide, potassiumethoxide, and other alkali metal alkoxides and quaternary ammoniumcompounds such as benzyl trimethyl ammonium hydroxide.

The amount of catalyst may be quite small, ranging from about 0.1% to10% or more, based on the weight of the isomelamine that is to beisomerized. In the event that the solvent contains acids, or acidicsubstances, or that acid. salts of the isomelamines are used as startingmaterials, enough of the alkaline substance should be used to neutralizethe acid or acid-forming substances present and provide an excess of thealkaline material for catalyzing the isomerization.

Although the isomerization will take place at a fairly good rate at 80C. a much faster rate of isomerization is obtained at temperatures of100 C. or higher. Actually, in most cases the temperature of the processwill be governed by the refluxing temperature of the hydroxylatedsolvent chosen. Higher temperatures may be used if the reaction iscarried out under pressure. The maximum temperatures depend, of course,upon thedecomposition temperature of the solvent, the intermediate orproduct.

. My invention will now be illustrated by means of the followingexamples in which representative isomelamines are isomerized to thecorresponding normal melamine in the presence of different catalyticagents and in various solvents and solare not limited to the specificdetails described herein.

moving samples, was placed a mixture of 21 cc. (0.21 mol) of butylamineand 100 cc. of Cellosolve (beta-ethoxyethanol) which had beenneutralized with a portion of a mixture of 10 g. of sulfric acid in 25cc. Cellosolve. To this was added 46.8 g. (0.2 mol) of crudemono-potassium, 1,3-dicyanoguanidine and the flask heated with an oilbath. When the liquid temperature had reached 114 C. the rest of theacid Was added at such a rate that a sample of the liquid remainedfaintly blue to bromthymol blue. Further acid (10 g. of sulfuric acid in25 cc. Cellotime the temperature was gradually raised to 130 C. Theliquid now no longer turned the indicator blue so the last portion ofthe acid was added very slowly during the next two hours. The vaporsduring this time were always alkaline.

After standing over night the solid was filtered,

20 cc. of 50% sodium hydroxide, stirred while in an ice bath, filtered,and washed with ice water. After drying in the vacuum desiccator therewas obtained 28 g. or a 77% yield of butyl isomelamine which decomposedat 230-23l C.

To a solution of 0.3 g. of metallic sodium dissolved in 100 cc, ofbutanol was added g. of butyl isomelamine. The mixture was heated unthehot butanol. The solution was then neutralized with acetic acid and thebutanol evaporated under reduced pressure. The gummy solid,

have a melting point of 160-162 C. The mixed melting point with anauthentic sample of butyl melamine was at the same temperature.

Example 2 tained was recrystallized from methanol conof water. Itsmelting point was found to be 110 C. The hydrochloride and Example 3 Toa solution of 0.57 g. (0.026 mol) of sodium metal in 100 cc. of butanolwas added 4.66 g.

(0.0226 mol) of beta-hydroxyethyl isomelamine hydrochloride. The mixturewas heated under a reflux condenser for three and a half hours withvigorous mechanical stirring. After the solution had been neutralizedand the butanol removed under reduced line whereupon a precipitateformed slowly. This product was found to soften at 2 5 C. and decomposeat 270 C. It appeared to be beta-hydroxyethyl melamine with a smallamount of the isomelamine. After filtering the solution again andallowing it to stand overnight, a small amount of pure beta-hydroxyethylnormal melamine precipitated. This product melted without decompositionat 223-225 C. and was found to be identical with a known sample of thecorresponding normal melamine which had been prepared by another method.

Earample 4 In a three-necked flask, bath, and fitted flux condenser anddropping funnel was placed 21.5 g. (0.22 mol) of aniline. To this wasadded 50 cc. of water, one-half of a diluted acid made by mixing 35 cc.concentrated hydrochloric acid with cc. of water, and 29 g. (0.2 mol) ofmono- 1,3-dicyanoguanidine. When the temperature had reached 92 (3., thesolution was clear and the rest of the diluted acid was added dropwiseduring the next one-half hour. Frequent tests with pH paper showed thepH remained in the region 3 to 4 until all but the had dropped to aboutone and remained there for 5 minutes.

quantitative. After recrystallization from water, it decomposed at 318C.

Phenylisomelamine was prepared by adding Example 6 2 g. ofpara-nitrophenyl isomelamine was re- About I g. of 2,5-dichlorophenyli;isomelamine was; suspended. in 5.0 cc. of; butanol. which. con.- tained"a catalytic: amount of sodium. butoxi'dle. Upon refluxing; theisomelamine dissolvediwithin a few minutes but refluxing was continuedifor three hours: The solution was then neutralized with acetic acid andthe butanol evaporated to leave normal. 2,5 -dichlorophenyl melamine asa white solid, melting without decomposition at 22'3-225 C.

Example 8 One pellet of KOH was dissolved in 50 cc. of butanol and 15 g.of phenyl isomelaminewas-then added. The mixture was refluxed for threehours, after' which the solution was neutralized and the butanolevaporated. Normal phenyl melamine was obtained in an 80% yield.

Example 9 nium hydroxide was dissolved in 58 cc. of butanol. 10 g. ofphenyl isomelamine was then added and the mixture refluxed for fourhours. The solution was then neutralized with acetic acid and phenylmelamine was obtained with a yield of 82%.

Example 10 10 g. of phenyl isomelamine was dissolved in 50 in which R isas defined above, an alcohol, and catalytic amounts of a strongly basicsubstance at temperatures of at least 89 C. until the isomelamine hasbeen isomerized to a normal mel- 6 amine;.. and: recovering; the: thustermed. normal monosubstituted. melamine.

2. A method of preparing. normal mOXIOSLlbSti-r tuted melamines havingthe formula monosubstituted isomelamine having the formula r'rn in:which R is; as defined above, an alcohol, and catalytic; amounts of an:alkali metal alkoxide at temperatures ofat least: 80 C-.. until the;isometarn-ine has been: isomerized. to normal melamine and recoveringthe thus formed normal monoaromatic-substituted melamine 3. A method.of. preparingv normalv monnphenyl melamine which comprises heatingtogether as the essential components monophenyl isomelamine, an alochol,and catalytic amounts of a strongly basic substance at temperatures ofat lease 80 C. until the monophenyl isomelamine 1 cc. of 50% solution ofbenzyltrimethylammohas been isomerized to normal phenyl melamine andrecovering the thus formed normal monophenyl melamine.

4. A method of preparing normal monododecyl H melamine which comprisesheating together as the butanol removed by evaporation. Normal theessential components monododecyl isomelamine, an alcohol, and catalyticamounts of a strongly basic substance at temperatures of at least 80 C.until the monododecyl isomelamine has been isomerized to normal dodecylmelamine and recovering the thus formed normal dodecyl melamine.

5. A method of preparing normal monosubstituted melamines having theformula NH: in which R. is a radical of the group consisting ofaliphatic and aromatic radicals which comprises heating together undersubstantially anhydrous conditions as essential components amonosubstituted isomelamine having the formula in which R. is as definedabove, an alcohol, and from 0.1 to 10% by weight based upon the weightof the said isomelamine of a basic substance at least as strongly basicas the said isomelamine until the isomelamine has been isomerized to anormal melamine, and recovering the thus formed normal monosubstitutedmelamine.

6. A method of preparing normal monosubstituted melamines having theformula 11TH: in which R is a radical of the group consisting ofaliphatic and armoatic radicals which comprises heating together undersubstantially anhydrous conditions as essential components amonosubstituted isomelamine having the formula I THz in which R. is aradical of the group consisting of aliphatic and aromatic radicals whichcomprises heating together under substantially anhydrous conditions asessential components a monosubstituted isomelamine having the formula inwhich R is defined above, the monoethyl ether of ethylene glycol, andfrom 0.1 to 10% by weight based upon the weight of said isomelamine of abasic substance at least as strongly basic as the said isomelamine untilthe isomelamine has been isomerized to a normal melamine, and recoveringthe thus formed normal monosubstituted melamine.

JACK T. THURSTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,197,357 Widmer Apr. 16, 19402,328,825 McMahon Sept. 7, 1943

